Recently, networking and multi-function of various devices used in a production site are improved with the progress of Information and Communication Technology (ICT). Specifically, there has been put into practical use a system in which a control device such as a programmable logic controller (PLC), an input/output (I/O) device such as a sensor and a relay, and an actuator such as an inverter and a motor driver are connected and integrated through a network.
Various log output functions are mounted on the control system such that a malfunction generated during a system configuration or a system running can be investigated ex post facto. For example, Japanese Patent Unexamined Application No. 2015-176370 discloses a control system that can easily recognize a state of the control device during generation of a factor of an event.
In the networking and multi-functionalized control system, the network itself and the device and unit connected to the network are correlated with each other, and it is necessary to comprehensively study network topology and data use relationship between devices connected to the network in the case that some abnormal factor is generated. There is a demand for easily specifying the factor of the malfunction or abnormality, which is generated in the control system including the network.